We see the moon because the sun's light reflects off it. So the phases change depending on how much the sun reflects of it. The moon circles around the Earth so at certain times there will be a full moon and at certain times a new moon and everything in between.
Hasan most likely has rickets
Rickets is a disease of children which is caused by vitamin D deficiency. Rickets softens and weakens bones in affected children. Symptoms of rickets include bowed legs, pain in the bones, stunted growth, trouble sleeping and muscle weakness. Rickets can lead to other health problems such as intellectual disability and muscle spasms.